Chemistry

We Got the Blues
Humanity's obsession with a certain color

When we finally get around to writing the entire story of civilization, we'll devote a chapter to the color blue. Sure, children around the world choose red as their favorite color. But that's just a phase, like tearing the crust off bread. Make no mistake: Blue rules.

For thousands of years humans have found ingenious ways to turn things blue. In the ancient Mediterranean, biblical blue dye came from a hermaphroditic snail with a gland that generates a fluid that becomes blue when exposed to air and light—at least when the mollusk is feeling masculine. "They had to extract the glands when the snails were more male than female," explains Tony Travis, a historian and chemist at Jerusalem's Hebrew University.

Another blue dye came from a plant called woad. Its leaves had to be ground and fermented before the pigment emerged. Celts painted their bodies with it (think Mel Gibson in Braveheart). Medieval scribes illustrated manuscripts with it.

The blue in woad came from a molecule scientists refer to as indigo. But woad wasn't the best source of blue. Another plant—also known as indigo—produced the color more effectively. Indigo plantations sprawled across Asia, while woad lost luster.

Eventually synthetic dyes replaced natural ones. In 1897 the Germans manufactured the first synthetic indigo from coal-tar derivatives. Synthetic dyes triggered an explosion of blue fashions in the 20th century. Policemen switched from black uniforms to blue. The blue blazer replaced the black suit. And in the 1950s blue jeans took off, radiating youth and rebellion.

Next up: biotech blue. When Australian toxicologist Elizabeth Gillam was studying bacteria implanted with human DNA, her cultures unexpectedly turned blue. She suspected a mold contamination. But after conferring with Fred Guengerich, a colleague at Vanderbilt University, Gillam realized she'd stumbled onto something wonderful: The bacteria were producing the indigo molecule as part of their metabolism. "This is a good lesson for student scientists," says Gillam. "If something looks bizarre, don't discount it. It might be much more interesting than the result you expected."

Biotech indigo could be used to create blue plant tissues, including flower petals (imagine a perfectly blue rose). Scientists speculate that the process might even yield blue cotton, which would mean your jeans wouldn't need any dye. But then how would we ever get that nice faded look?

—Joel Achenbach
Washington Post staff writer